. >> reporter: four years ago biden's challenge was not to appear overly aggressive with sarah palin. this time around democrats want him to do the opposite, come out swinging but with a concise message. former michigan senator jennifer played the role of palin. >> the big challenge for someone like joe biden, he is a so glib and so good at listening to people is delivering a message inside of a structured format. >> reporter: now with all the attention as these two men take the stage, there's one interesting thing. gallup's been doing some polling over the years. since 1976 eight vice presidential debates these guys performance's sarah palin's of course, too, did not have any impact on how people voted in the ballot box. so i guess that doesn't stop the pressure though, charlie. >> jan crawford, thank you. with us now, david axelrod, senior strategist for the obama campaign. good morning. >> good morning, charlie. >> the president said the stakes are high in all of these debates and you were part of the team helping prepare vice president biden. how is his preparation different than